Who is Soledad - evil Grandmother from Caramelo, or, Puro Cuento: A Novel and what is their importance?

Soledad is the evil Grandmother. At the beginning she is the mean grandmother that makes all of the daughter-in-laws miserable. She is harsh, blunt, and overly dramatic. When we read her story, however, there is a reason she is so harsh. Her mother died when she was very young, and her father remarried, sending her away to live with and work for her aunt. She was pawned off to the Reyes family where she became the household servant and personal caregiver of Eleuterio and Narciso.